Produção de coquetel enzimático rico em endoglucanase termoestável em biorreator de leito empacotado e sua aplicação na obtenção de nanocelulose

Abstract

Nanocellulose is a bioproduct with high added value obtained through the conversion of lignocellulosic biomass. Due to characteristics such as high aspect ratio, low toxicity, thermal stability and high crystallinity, nanocellulose has several applications. Obtaining nanocellulose through the enzymatic route stands out for being an environmentally friendly method, however studies are necessary to improve the efficiency of this process. In this sense, the use of an enzymatic cocktail with thermostable properties can be an interesting strategy for obtaining nanocellulose. In this work, the objective was to use the packaged bed bioreactor for the production of thermostable enzymatic cocktail and apply the enzymes to obtain nanocellulose. To obtain this cocktail, the thermophilic fungus M. thermophila was cultivated by fermentation in solid state on a small scale using full factorial design varying the bagasse mass, soybean meal fraction and moisture. The selected cultivation conditions were replicated in a multilayer-packaged bed bioreactor. The enzymes were then used to hydrolyze cellulose pulp at temperatures of 50, 60 and 70 °C and convert the substrate into nanocellulose. The enzymatic extracts of the fungus M. thermophila obtained both on a small scale and in bioreactor showed the activities of endoglucanase around 200 U/g-substrate. The hydrolysis of the pulp performed at 60 °C showed better results, converting 60% of the cellulose, with yield of 16.2% of nanocellulose with 96 hours of hydrolysis. The nanomaterials obtained presented crystalline index of 77.4%. By FTIR it was possible to verify that the chemical compositions of the nanomaterials obtained were nanocellulose. On set temperatures were 152 to 194 °C. Atomic force microscopy showed that the obtained nanocrystals had an average length of 157 nm and an aspect ratio ranging from 1.1 to 10.0. Although the yield of nanocellulose is still lower when compared to that of acid hydrolysis, advances in enzymatic hydrolysis can still be obtained, investigating other possible enzymes that degrade lignocellulosic biomass, such as oxidative enzymes.